This invention relates to a plastic molding, for use for example as a case (box) for a piece of acoustic equipment containing a speaker, which has multiple holes passing from the inner surface to the outer surface for sound emission or ventilation, etc., and a method for manufacturing the plastic molding and a mold for manufacturing the molding.
Among for example acoustic equipments containing loudspeakers, of those having a construction in which a box and a speaker baffle are made as one plastic molding, most have holes for sound emission opened in the part of the box in front of the speaker and also have net for protecting the speaker fitted as a speaker baffle over the area where the sound emission holes are.
Other types do away with the speaker protecting net, and incorporate a net like area into the plastic molding as the speaker baffle instead. This approach is effective for products in which the speaker part is to be emphasized as an aesthetic feature, but for products in which it is desirable that the speaker be hidden this approach is not suitable and in practice a speaker protection net is used.
FIG. 3 is an outline cross-sectional view of the locality of the speaker in a conventional plastic molding of this kind used as the case (box) of an acoustic equipment containing a speaker. In FIG. 3, reference numeral 1 denotes the speaker; 2 denotes the molded plastic box; 3 denotes the through holes for sound emission formed in the box 2; 4 denotes a spacer wall formed on the inside surface of the box 2 around the through holes 3; and 5 denotes a sound chamber formed by the speaker 1, the box 2, and the spacer wall 4. Reference numeral 6 denotes a baffle mounted on the outer surface of the box 2 and covering the through holes 3 for speaker protection and aesthetic improvement. In this kind of conventional plastic molding, in forming the through holes in the box it is not possible to make the internal diameter of the holes small; the holes in the box are conspicuous, the appearance of the exterior of the box is spoiled, and it is therefore necessary to use a covering net or the like to keep the holes out of sight.